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By Suja Mary James with inputs from Dr Partha Jyoti Das
India is a subcontinent encircled by oceans on three sides, making it particularly vulnerable to cyclones. However, the east coast is more vulnerable than the west, particularly the east coast of Odisha, making it the most cyclone-prone of all the coastal states there. From 1999 to 2023, Odisha witnessed ten cyclones, from Paradip Cyclone(1999 Super Cyclone) to Cyclone Asani (2022). Of all the severe cyclonic storms in the Bay of Bengal, 15% affect Odisha’s cyclone-prone districts, including Balasore, Bhadrak, Jajpur, Cuttack, Puri, Ganjam, Kendrapara, Jagatsinghpur, Khordha, and Gajapati.
Observed and forecasted route of cyclone Asani(2022) along the Bay of Bengal.
Source: weather.com
Even in the early phases of their formation, cyclones pose one of the most significant risks to property and human life. They include a wide range of risks, such as storm surges, flooding, extremely strong winds, tornadoes, and lightning, each of which can potentially have a severe negative impact on life and property. When these risks are combined, they interact with one another, considerably raising the risk of fatalities and property damage.
What are Cyclones?
Cyclone is a general term for a low-pressure system over tropical or sub-tropical waters that has organized convection (i.e., thunderstorm activity) and winds at low levels that circulate either clockwise (in the northern hemisphere) or anticlockwise (in the southern hemisphere). They usually develop when the sea surface temperature is higher than 26.5 °C. Tropical cyclones can last for days or even weeks and have irregular trajectories. If it passes over land or cooler waters, a cyclone will dissipate.
Depending on where they originate in the world, tropical cyclones are referred to by various names. In the Caribbean Sea and the North Atlantic Ocean, it is known as a hurricane, while in the western North Pacific, it is known as a Typhoon. It is referred to as a tropical cyclone or just a cyclone in the Indian Ocean region and the South Pacific Ocean. Since they virtually invariably form between the Tropics of Cancer and Capricorn, all these storms are classified as tropical.
Tropical cyclones form over water that is warmer than 26.5℃. As the air warms up, it rises quickly, forcing incoming air to replace it and resulting in strong wind currents and stormy weather conditions. A downdraft of colder air and heavy rain ensues from the fast ascending humid air cooling and condensing. The Coriolis effect, which is the result of the Earth’s rotation, causes cyclonic rotation. Tropical cyclones typically do not form within five degrees north or south of the equator because the Coriolis effect is less pronounced along the equator.
Source: sites.google.com
Tropical cyclones are classified according to their greatest sustained wind speed. Tropical depressions, which have wind speeds between 25 and 38 miles per hour, are the precursors to cyclones. The mechanism is fueled by cyclonic motion and warm temperatures. A storm is upgraded to a tropical storm when its sustained winds exceed 39 to 73 mph. A storm is deemed to be a hurricane when its sustained winds exceed 74 mph.
Source: WMO
The Impact of Climate Change
According to Chen et al. (2021), the Earth’s climate system has experienced measurable anthropogenic warming for the past 50 years. Numerous modeling studies have suggested that this warming may significantly affect Tropical Cyclones. Moreover, observations indicate that the number of severe Tropical Cyclones (TCs) is intensifying globally, especially from ocean warming, which can generate more energy and greater potential intensity.
Possible effects of anthropogenic climate change include an increase in the proportion of severe TCs (categories 4 and 5). It is predicted that this percentage of intense TCs would rise even more, resulting in an increased number of storms with more destructive wind speeds, higher storm surges, and more extreme rainfall rates. The majority of climate model studies predict a commensurate decline in the percentage of low-intensity cyclones, therefore the annual total of TCs is predicted to decline or stay roughly the same.
According to IPCC AR6 model forecasts for a 2℃ global warming, tropical storm intensities are expected to increase globally on average (with medium to high confidence) by 1 to 10%. If there is no decrease in storm magnitude, this change would indicate an even greater percentage rise in the destructive potential per storm. Also, due to global warming and the ensuing rise in atmospheric moisture content, tropical cyclone rainfall rates are predicted to increase in the future (medium to high confidence). Modeling studies often indicate an increase in rainfall rates between 10 and 15 percent within 100 km of the storm.
The wet points are particularly alluring to tropical cyclones. The eastern plain is more vulnerable to cyclones since there are more wet points along the east coast than the western plain. The mighty Western Ghats on the west coast obstruct tropical cyclones, which go from high-pressure levels above the sea to low-pressure areas over the land. While the Eastern Ghats are there, their strength is insufficient to stop cyclones from moving across them. Hence, due to minor geographic differences between the eastern and western coasts, tropical cyclones are more likely to affect our eastern beaches.
The growth of populated areas and vital infrastructure along coastlines, tropical cyclone vulnerability is increasing globally. The frequency of cyclonic activity over the Bay of Bengal is five times greater than that over the Arabian Sea. The BoB has experienced an increase in tropical cyclonic activity over the past 122 years (1877–1998), according to Singh et al. (2000). As a result, compared to the Arabian Sea, the States bordering the Bay of Bengal are more susceptible to tropical cyclones.
What do experts say?
Dr. Partha Jyoti Das, Head, ‘Water, Climate & Hazard Division,’ Aaranyak (A Scientific and Industrial Research Organisation of India) and Inhouse Expert, CFC, said, “Tropical Cyclones are accompanied by very violent winds, torrential rain, high waves and, in some cases, very destructive storm surges and coastal flooding. They put tremendous stress on coastal areas by affecting the natural mode of winds, waves, air and seawater circulation, tidal effect, and flooding. Cyclones in the Indian coastal zones are also known to have been enhanced in frequency and magnitude due to climate change. As population density and economic investment grow rapidly, there is a genuine concern about the increased destructive potential of tropical cyclones along the Odisha coast.”
Indian Coatlines Prone to Cyclones
Over 7,516 km of India’s coastline, of which 5,400 km are on the continent, are exposed to cyclones with varied intensities and frequencies. Although the North Indian Ocean (the Bay of Bengal and the Arabian Sea produces just around 7% of the world’s cyclones, or 5 to 6 tropical cyclones annually, their impact is comparatively significant and catastrophic, especially when they strike the shores surrounding the North Bay of Bengal. Tropical cyclones affect the country’s thirteen coastal states and Union Territories. Of these, four states—Tamil Nadu, Andhra Pradesh, Odisha, and West Bengal—as well as one UT—Pondicherry on the east coast—and one state—Gujarat on the west coast—are more vulnerable to cyclone hazards than the others.
Dr. Das pointed out that- apart from cyclones, coastlines are vulnerable to erosion and accretion. Dr. Das states, “Erosion and accretion are two natural processes that regularly occur in coastal areas anywhere in the world affecting the configuration and shape of the coastline and unleashing various impacts on coastal human societies and ecosystems. However, in this age of unescapable environmental and climatic changes, such processes are also significantly affected by anthropogenic activities”.
Almost all the world’s coasts experience erosion or accretion as a result of different natural and man-made factors. The Indian coastline on either side of the peninsula and the islands is subject to various coastal processes, making the coast susceptible to erosion. The loss of land or the removal of beach or dune sediments due to wind, wave action, tidal currents, wave currents, drainage, and different coastal development activities is known as coastal erosion. Waves produced by winds, storms, and other exceptional weather conditions can cause coastal erosion on a long-term basis or only temporarily by shifting sediments. Storm surges, monsoonal high waves, and tsunamis are all short-term causes of coastal erosion. Erosion in one location could cause accretion in the surrounding area. Wind-wave direction, tidal range, geomorphological setting, groundwater fluctuations, sea level changes, and weather/climate conditions influence coastal erosion.
Causes and consequences of coastal erosion
Dr. Das explained the plausible factors that degrade the coastal ecosystem. According to him, “the coastal zones of India, especially the eastern coastline is affected by natural factors like various wind patterns that produce storm charge, sea waves, sea water circulation driven by winds, tide, and tidal current, tidal flooding as well as tsunamis generated due to earthquakes in and around oceans and seas. Similarly, the sediment load and mode of sediment transport into the sea from freshwater and marine sources also affect the mechanism of erosion and accretion”.
“At the same time, human activities like infrastructure development, mining, urbanization, construction of embankments, harbors, ports, and dams, and changes to the natural influx of flow and sediment due to interventions on associated river systems also can have a remarkable bearing on such coastal processes. Climate change that causes sea level rise, seawater ingress, and intensifies storms and coastal flooding has become another driver of change for the coastal ecosystems, hydro morphology, and human habitats,” Dr. Das added.
According to the National Centre for Coastal Research (NCCR) study, of the Indian coastline, 33.6% was at risk of erosion, 26.9% was accreting (expanding), and 39.6% was in a stable state. Using multi-spectral satellite photos and field survey data, the NCCR has observed shoreline changes throughout the Indian coastline for the past 28 years (1990-2018). In terms of Odisha, 280.02 km, or 51%, are under accretion (growing), and around 128.77 km, or 23.4% of the coastline, are stable.
The secondary impact of coastal erosion should also be considered. Dr. Das also spoke about the hidden threats of coastal erosion. “It is to be noted that the Odisha coastal zone has highly valuable industrial areas (such as Chandipur, Paradip, and Gopalpur ports) as well as natural ecosystems. The Gahrimatha Marine Sanctuary (Kendrapara District) and the Rushikulya river mouth (Ganjam District), famous as the world’s largest nesting sites of the endangered Olive Ridley Sea Turtles, and the Bhitarkanika National Park, (Kendrapara District) well-known habitat of the endangered saltwater crocodile and the second largest mangrove in India, are extremely important coastal biodiversity areas. The Chilika Lake, a Ramsar Site is Asia’s largest brackish water lagoon and an important source of livelihood for about 20 lakh fisherfolks. Therefore, erosion risk borne by these coastal areas can result in heavy economic and ecological loss and damage”.
Coastal erosion in Odisha
Dr. Das added, ” Odisha has historically been a hotspot of TCs due to its physiographic setting, geographical location, and topography. The relatively flat landmass, absence of a topographic barrier, and intrusion of atmospheric disturbances from the Pacific region, all these factors enable most of the TCs to flow northwestward and enter, pass over, or landfall in Odisha making it the most cyclone-affected state in India. The state was hit by about 110 cyclones between 1891 and 2018. In the last 12 years, the state has experienced as many as 10 cyclones. The most disastrous among the recent ones are the super cyclone in October 1999; the TC Phailin in October 2013; TC Hudhud in October 2014; TC Titli in October 2018 and the extremely severe cyclonic storm Fani in May 2019”.
Odisha has been severely impacted by climate change for the past few years. Researchers from seven universities conducted a study that found sea force is growing more potent as a result of a significant decrease in the volume of water and sediment flowing through the state’s main rivers. In the next three decades, the researchers predicted that 55% of the 480 km of the shoreline might experience accretion while 45% will experience erosion. According to them, Odisha’s shoreline will erode over 200 km by 2050 if the pattern persists.
The study, “Quantitative assessment of the present and future potential threat of coastal erosion along the Odisha coast using geospatial tools and statistical techniques,” found the erosion hotspots. As per the study, Boxipalli and Podampeta in Ganjam and the Pentha and Satabhaya coast in Kendrapara had the highest levels of erosion between 1990 and 2020, those regions along with Chandrabhaga Beach and the Subarnarekha estuary will experience even greater erosion.
According to the research, Boxipalli’s shoreline has retreated by about 38 meters since 1990, and that distance is predicted to rise to about 57 meters soon. The coastline of Podampetta has shifted 52.36 m since 1990, and by 2050 it is expected to rise by another 44 m. The shoreline has already retreated by about 67 m at Baliapanda Beach in Puri, and this process is predicted to continue. Along the 68-meter-long Chandrabhaga beach, erosion is seen to be trending similarly. The Satabhaya shoreline moved 210 m and Pentha beach deteriorated by 490 m in the last 20 years. The area from Chandipur to Subarnarekha in the Balasore district is even more vulnerable because both places have previously shown a trend of erosion with distances of about 40 and 660 meters, respectively.
As per the recent NCCR report, the state has seen coastal erosion in six coastal areas (Balasore, Bhadrak, Ganjam, Jagatsinghpur, Kendrapara, and Puri) along with regular tropical cyclones and floods. Official statistics indicate that of Odisha’s 480 km of coastline, 267 km have experienced sea erosion or accretion. Based on satellite images from 2006 to 2018, the Odisha Space Applications Centre (ORSAC) conducted a DGPS survey on 3,555 sq. km. of coastal areas. According to the survey, there was accretion on 1,582 hectares of shoreline, whereas 2,489 hectares of land in the six coastal districts were subject to erosion.
Kendrapara district has the maximum amount of accretion and erosion (1,058 ha), followed by Balasore district (920 ha), Jagatsinghpur (679 ha), Bhadrak (543 ha), Puri (540 ha), and Ganjam (1,040 ha) (327 ha). The Kendrapara district in Odisha is the most severely affected by sea erosion, with 16 of the area’s villages already submerged in the sea and 247 people facing eviction as a result of the sea level’s rise.
Dr. Das explained structural measures to reduce the impacts caused by tropical cyclones and coastal erosion. “The effect of climate change on TCs is complex and not fully understood. Scientists have observed TCs getting modified in different ways due to a warming climate, for example, sometimes increasing in the number of events and frequency, but also with decreasing incidence with less frequency at other times; quick intensification from weaker storms to stronger storms and increase in rainfall, storm surge and flooding in the coastal areas. A number of structural measures such as breakwaters, sea walls, groynes, flood embankments, etc. are adopted in general to protect the coastline from erosion and flooding hazards. Recently geotextile-based tubes have been used to prevent erosion of the shorelines in Odisha and other coastal states in India. Such measures, at times, may be expensive and may have adverse effects on the coastal ecosystems and populations”.
Under the Integrated Coastal Zone Management project, the government of Odisha has created a coastline management plan. According to the plan, coastal erosion has occurred or could occur in the Satabhaya area of the Kendrapara district, Talasahi, Udayapur, the northern side of Budhabalanga in Balasore, the Paradip port area of Jagatsinghpur, the bank of the Jamuna, the beach areas of Puri, the northern part of Gopalpur port, and the north of Bahuda river in Ganjam.
Integrated Coastal Zone Management project
Mitigation methods try to lessen the impact of cyclones on life and livelihood. Under the Integrated Coastal Zone Management project, the government of Odisha has created a coastline management plan. Under the sponsorship of the World Bank, the Integrated Coastal Zone Management Project (ICZMP) has been put into action along two segments of the Odisha coast: Gopalpur to Chilika and Paradeep to Dhamara. By building 14 Multifunctional Cyclone Shelters (MCS) within the project region, OSDMA has strengthened the community by giving corpus funds, standardized emergency supplies for shelters, and increased capacity via various trainings—all without causing environmental or social harm. The estimated project cost was Rs. 14.60 crores.
Therefore, it is essential to explore eco-friendly and nature-based solutions such as increasing vegetation cover of the coastal areas and sand dunes and restoration and conservation of mangrove forests, which have far less environmental impact. The local people’s traditional knowledge and skills can also add value to such mitigatory strategies. A judicious combination of structural and non-structural measures can also be an option for more sustainable coastal protection. Improved knowledge about how both climatic and non-climatic factors collude and contribute to the increasing land erosion and subsidence in the coastal areas is needed for policymakers and scientists to figure out more effective policies and measures”.- Dr. Das Concluded.
There are a variety of strict protective measures in place to deal with the issues; however, they may lessen the recreational value and natural dynamics of the shoreline. Soft defenses have the potential to preserve the recreational value and the natural dynamics of the coast, but they frequently need ongoing maintenance. In many instances, combating coastal erosion requires striking a balance between the many interests and concerns as well as a suitable combination of hard and soft management approaches.
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References:
https://magazines.odisha.gov.in/Orissareview/2016/Jan/engpdf/38-42.pdf
https://www.frontiersin.org/articles/10.3389/feart.2021.769005/full
https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/
https://magazines.odisha.gov.in/Orissareview/2016/Jan/engpdf/38-42.pdf
https://www.osdma.org/integrated-coastal-zone-management-project/#gsc.tab=0
https://www.fao.org/3/ag127e/ag127e09.htm
https://www.sciencedirect.com/science/article/abs/pii/S004896972301104X
